We are naturally omnivores, we have enzymes in our bodies that are only present in omnivorous or carnivorous animals designed primarily for digesting meat. Therefore we are born with the ability to eat and digest meat.
However, our evolutionary background was shaped much longer by herbivorous creatures than ones that ate meat. Our intestinal tract is tremendously long and our bodies react similiarly to a herbivorous creature's to meat - we develop atherosclerosis, become somewhat more susceptible to some forms of cancer, are more likely to get heart disease. If you dissect a carnivorous animal's heart, their major arteries, and take a good look, you'll find that their bodies don't really develop sedimentary deposits of cholesterol and fat. Their bodies are developed for a meat-intensive diet. We, like herbivorous animals that are forced to eat meat in experiments, develop serious conditions much more easily, develop heart disease at a rate incomparable to other omnivores and to carnivores.
Therefore I think that eating as much meat as we do is a learned thing, mostly because people are either uneducated about what it can do to your body or they have an apathy or lack of insight as to how most meat on the market is "made". Unlike making plastic cups on a conveyor belt, which can be done in a sterile and cold unfeeling environment, genetically breeding, raising and slaughtering animals in such a way shows disregard for a natural ecosystem and for the sentient nature of most of the food animals we devour senselessly.
I believe that we are designed to be able to eat meat, maybe as a garnish, maybe to survive, on occassion. But we are not designed to eat meat ANYWHERE NEAR as much as we do in a Western diet. Our diets should be overwhelmingly, if not completely, made up of plant foods. Just because we can eat meat and live through it doesn't mean it doesn't add up, that it is justifiable to what it reflects upon our society, our impact on the environment, and our own personal health.
Sure, 'cavemen' ate it, but their life expectancy was what - 30 years? 40 years? What did they die of? They didn't have the life span we do now, where the consequences of a poor diet become very evident once you reach 50, 60 years of age. We also have an unnatural system for acquiring meat, and our meat is full of chemicals and toxins now that weren't present even a hundred years ago.
For those like me, with a direct ethical opposition to eating meat, a plant-based diet is almost easy, effortless, undeniably good for my body when compared to a traditional American diet that is loaded with four, five servings of meat a day (look at portion size - is your chicken breast the size of a deck of cards? It's more likely the size of your whole hand). While everyone in my family is stricken with diabetes, obesity, heart disease and other serious conditions, I remain the only person from my generation in my family that has remained relatively healthy on all aspects, with the occassional cold but no chronic diseases.
Source(s):
Vegan SA - South African Vegans Directory Listings